Nominal 601: Assignment Paper

STAT 601 – Assignment #4 (Due 06/29/14) (80 pts.)

Review the following materials:
1) Narrated Powerpoint Lectures Comparing Two Populations with a Numeric Response a) independent samples b) dependent samples

Comparing Two Populations with a Nominal/Categorical Response
a) independent samples (z-test, Fisher's Exact test, CI’s for RR & OR)
b) dependent samples (FYI ONLY – NOT ON ASSIGNMENT) 2) Non-narrated Powerpoint Lectures (same as above)
3) Lecture Handouts 9 – Statistical Inference sections 9.5 – 9.8 only.
4) JMP tutorials below by the Assignment 4 link.
JMP Demo - Two Sample Pooled t-Test
JMP Demo - Two Sample Non-pooled t-Test
JMP Demo - Paired t-Test

RESEARCH ARTICLE
REVIEW PROBLEMS

1) Use Table VI in the paper entitled “Perceived Coping MI” answer the following questions.
a) Were the groups in this study independent or dependent? Provide a rationale for your answer.
b) Examine the t-ratios (i.e. t-statistics) in Table VI. Which t-ratio indicates the largest difference between the males and females post MI in this study? Is this ratio significant? Provide a rationale for your answer.
c) What is a Type I error? Is there a risk of Type I error in this study? Provide a rationale for your answer.
d) The authors reported multiple df (degrees of freedom) values in Table VI. Why were different df values reported for this study?
e) What does the t-value for the Physical Component Score tell you about men and women post MI? If this result was consistent with previous research, how might you use this knowledge in your practice?

2) Using the article labeled “Transfer Anxiety MI” answer the following
questions.
a) The baseline anxiety and information scores were not significantly different between the experimental and comparison groups. What does this mean? Does this strengthen or weaken the results of the study? Provide a rationale for your answer.
b) The results indicated a statistically significant difference between the anxiety score for the two groups of patients (t=3.875, p 4 ng/ml).
Of these, 46 were diagnosed as having cancer. Ten of the 57 men with PSA values < 4 ng/ml had cancer. On the basis of these data may we conclude that, in general, men with elevated PSA values are more likely to have prostate cancer? Let = .01.

Use inferential based upon the standard normal and Fisher's Exact Test to test the hypothesis of interest. Data File: PSA-Cancer.JMP
a) Standard normal test and CI for the difference in the population proportions. (4 pts.)
b) Fisher's Exact Test (2 pts.)
c) Summarize your findings. (2 pts.)

6 – HIV Status & IV Drug Use History of Women in NY Prison System
In a study of HIV infection among women entering the New York State prison system, 475 inmates were cross-classified with respect to HIV seropositivity and their histories of intravenous drug use. The variables you will be working with are coded as follows:

• IV Drug Use – indicator of previous intravenous drug use (Yes or No)
• HIV Status – results of HIV seropositivity test (positive or negative)

and the study results are contained in the data file: Prison HIV-Drug Use.JMP .

Research Question: Is there evidence that intravenous drug use is associated with HIV
seropositivity?

a) Among women who have used drugs intravenously, what proportion are HIV-positive? Among women who have not used drugs intravenously, what proportion are HIV-positive? (2 pts.)

b) Use Fisher’s Exact Test to determine if being HIV-positive is positively associated with a previous history of intravenous drug use for this population of women. State your conclusion along with a supporting p-value. (2 pts.)

c) Find a 95% CI for the risk difference and interpret. This difference is also referred to as the attributable risk (AR) = pexposed - punexposed. (3 pts.)

d) Use your answers to calculate the relative risk (RR) for being HIV-positive associated with intravenous drug use for this population of women. Also find a 95% CI for the RR. Interpret. (4 pts.)

e) Compute the odds ratio (OR) for being HIV-positive associated with intravenous drug use for this population of women. Also find a 95% CI for the OR. Interpret. (4 pts.)

f) Number Need to Harm (NNH) – Go to the following website which is actually the first hit when you Google Search: Number Needed to Harm.

http://en.wikipedia.org/wiki/Number_needed_to_harm

Read through the Wikipedia entry on this website and then find the Number Need to Harm for this study. (2 pts.)